2. 1. What is the Central Dogma? 2. How does prokaryotic DNA compare to eukaryotic DNA? 3. How is DNA organized in eukaryotic cells?

3. 1. Draw and label the 3 parts of an operon. 2. Contrast inducible vs. repressible operons. 3. How does DNA methylation and histone acetylation affect gene expression?

4. 1. List and describe the 3 processes that are involved in transforming a zygote. 2. Compare oncogenes, proto-oncogenes, and tumor suppresor genes. 3. What are the roles of the ras gene and the p53 gene?

5. Chapter 18

6. Transcription

7.  Bacteria need to respond quickly to changes in their environment ◦ if they have enough of a product, need to stop production  why? waste of energy to produce more  how? stop production of enzymes for synthesis ◦ if they find new food/energy source, need to utilize it quickly  why? metabolism, growth, reproduction  how? start production of enzymes for digestion STOP GO

8.  Feedback inhibition ◦ product acts as an allosteric inhibitor of 1 st enzyme in tryptophan pathway ◦ but this is wasteful production of enzymes = inhibition - -

9.  Gene regulation ◦ instead of blocking enzyme function, block transcription of genes for all enzymes in tryptophan pathway  saves energy by not wasting it on unnecessary protein synthesis = inhibition - - -

11.  Cells vary amount of specific enzymes by regulating gene transcription ◦ turn genes on or turn genes off  turn genes OFF example if bacterium has enough tryptophan then it doesn’t need to make enzymes used to build tryptophan  turn genes ON example if bacterium encounters new sugar (energy source), like lactose, then it needs to start making enzymes used to digest lactose STOP GO

12. Operon Operon: cluster of related genes with on/off switch Three Parts: 1.Promoter – where RNA polymerase attaches 2.Operator – “on/off”, controls access of RNA poly 3.Genes – code for related enzymes in a pathway

13. operatorpromoter DNATATA RNA polymerase repressor = repressor protein Operon: Promoter, Operator & Genes they control serve as a model for gene regulation gene1gene2gene3gene4 RNA polymerase Repressor protein turns off gene by blocking RNA polymerase binding site. 1234 mRNA enzyme1enzyme2enzyme3enzyme4

14.  Repressor protein ◦ binds to DNA at operator site ◦ blocking RNA polymerase ◦ blocks transcription ◦ Produced by regulatory gene

15. Regulatory generepressor Regulatory gene: produces repressor protein that binds to operator to block RNA poly

17.  Normally ON  Anabolic (build organic molecules)  Organic molecule product acts as corepressor  binds to repressor to activate it  Operon is turned OFF trp (tryptophan) operon  Eg. trp (tryptophan) operon

18. mRNA enzyme1enzyme2enzyme3enzyme4 operatorpromoter DNATATA RNA polymerase tryptophan repressor repressor protein repressor tryptophan – repressor protein complex Synthesis pathway model When excess tryptophan is present, it binds to trp repressor protein & triggers repressor to bind to DNA ◦ blocks (represses) transcription gene1gene2gene3gene4 conformational change in repressor protein! 1234 repressor trp RNA polymerase trp

19. What happens when tryptophan is present? Don’t need to make tryptophan-building enzymes Tryptophan is allosteric regulator of repressor protein

20. trp operon

21.  Normally OFF  Catabolic (break down food for energy) inducer  Repressor is active  inducer binds to and inactivates repressor  Operon is turned ON lac operon  Eg. lac operon

22. mRNA enzyme1enzyme2enzyme3enzyme4 operatorpromoter DNATATA RNA polymerase repressor repressor protein repressor lactose – repressor protein complex lactose lac repressor gene1gene2gene3gene4 Digestive pathway model When lactose is present, binds to lac repressor protein & triggers repressor to release DNA ◦ induces transcription RNA polymerase 1234 lac conformational change in repressor protein! lac

23. What happens when lactose is present? Need to make lactose-digesting enzymes Lactose is allosteric regulator of repressor protein

24. lac operon

25.  Repressible operon ◦ usually functions in anabolic pathways  synthesizing end products ◦ when end product is present in excess, cell allocates resources to other uses  Inducible operon ◦ usually functions in catabolic pathways,  digesting nutrients to simpler molecules ◦ produce enzymes only when nutrient is available  cell avoids making proteins that have nothing to do, cell allocates resources to other uses

26. Many stages

27.  Typical human cell: only 20% of genes expressed at any given time  Different cell types (with identical genomes) turn on different genes to carry out specific functions differential gene expression  Differences between cell types is due to differential gene expression

29. Chromatin Structure:  Tightly bound DNA less accessible for transcription  DNA methylation: methyl groups added to DNA; tightly packed;  transcription  Histone acetylation: acetyl groups added to histones; loosened;  transcription

31.  Modifications on chromatin can be passed on to future generations  Unlike DNA mutations, these changes to chromatin can be reversed (de-methylation of DNA)  Explains differences between identical twins

32. Transcription Initiation:  Control elements bind transcription factors  Enhances gene expression

33. Enhancer promoter activators Enhancer regions bound to promoter region by activators

34. Regulation of mRNA: micro RNAs (miRNAs) small interfering RNAs (siRNAs) micro RNAs (miRNAs) and small interfering RNAs (siRNAs) can bind to mRNA and degrade it or block translation

40. Section 18.4

41. 1. Cell Division: large # identical cells through mitosis 2. Cell Differentiation: cells become specialized in structure & function 3. Morphogenesis: “creation of form” – organism’s shape

43.  Cytoplasmic determinants: maternal substances in egg distributed unevenly in early cells of embryo

44.  Induction: cells triggered to differentiate  Cell-Cell Signals: molecules produced by one cell influences neighboring cells ◦ Eg. Growth factors

49. Section 18.5

50. 1. Proto-oncogene = stimulates cell division 2. Tumor-suppressor gene = inhibits cell division  Mutations in these genes can lead to cancer

51. Proto-OncogeneOncogene  Gene that stimulates normal cell growth & division  Mutation in proto- oncogene  Cancer-causing gene Effects:  Increase product of proto-oncogene  Increase activity of each protein molecule produced by gene

53.  Ras gene: stimulates cell cycle (proto- oncogene) ◦ Mutations of ras occurs in 30% of cancers  p53 gene: tumor-suppresor gene ◦ Functions: halt cell cycle for DNA repair, turn on DNA repair, activate apoptosis (cell death) ◦ Mutations of p53 in 50+% of cancers

54.  Cancer results when mutations accumulate (5- 7 changes in DNA)  Active oncogenes + loss of tumor-suppressor genes  The longer we live, the more likely that cancer might develop

55.  Embryonic development occurs when gene regulation proceeds correctly  Cancer occurs when gene regulation goes awry